Damping-driven time reversal for waves

Damping is usually associated with irreversibility. Here, we present a counter-intuitive concept to perform wave time reversal using a damping shock. A sudden and strong modification of the damping in time generates a time-reversed wave. In the limit of a high damping shock, this amounts to “freezing” the initial wave by maintaining the wave amplitude while canceling its time derivative. The initial wave then splits in two counter-propagating waves with identical profiles, but with time evolutions in opposite directions. We implement this damping-based time-reversal using phonon waves propagating in a lattice of interacting magnets placed on an air cushion. We show with computer simulations that this concept also applies to broad-band time-reversal in complex disordered systems.